Add remote agent distribution: install scripts + binaries

- agent.ps1: Windows one-line install script (irm u-claw.org/agent.ps1 | iex)
- agent.sh: macOS/Linux install script (curl -fsSL u-claw.org/agent.sh | bash)
- downloads/: agent binaries for Windows, macOS, Linux
- vercel.json: add Content-Type headers for binary downloads

vercel.json

@@ -1,3 +1,26 @@
 {
-  "outputDirectory": "website"
+  "outputDirectory": "website",
+  "headers": [
+    {
+      "source": "/downloads/agent.exe",
+      "headers": [
+        { "key": "Content-Type", "value": "application/octet-stream" },
+        { "key": "Content-Disposition", "value": "attachment; filename=agent.exe" }
+      ]
+    },
+    {
+      "source": "/downloads/agent",
+      "headers": [
+        { "key": "Content-Type", "value": "application/octet-stream" },
+        { "key": "Content-Disposition", "value": "attachment; filename=agent" }
+      ]
+    },
+    {
+      "source": "/downloads/agent-linux",
+      "headers": [
+        { "key": "Content-Type", "value": "application/octet-stream" },
+        { "key": "Content-Disposition", "value": "attachment; filename=agent-linux" }
+      ]
+    }
+  ]
 }